067-0681-01: Difference between revisions

067-0681-01 (view source)

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 The dynamic resistance of the tunnel diode in the high voltage state is low, but not
 low enough for the diode to be modeled as a rock-solid voltage source.
-It is approximated by
+It is approximated in theory by
 * r_d = 0.025V /  0.006 = 4.2 ohms
-The ringing current of a parasitic L-C resonator dissipating into
+Empirical measurements were closer to 7 ohms.
-the tunnel diode's dynamic resistance could result in significant
+This, plus the 43-ohm output resistor,
-time-domain voltage wiggles which would be difficult to distinguish
+makes for a 50-ohm output resistance when the tunnel diode is in
-from transient response problems
+the high-voltage state.  To prevent the 43 ohm output resistor from
-in the vertical amplifier of the oscilloscope under test.
+appearing inductive and spoiling the flat top of the output waveform,
+the resistor is actually
+mounted inside the BNC output connector.  The center
+conductor of the connector has a small hole to accept the 43 ohm
+resistor’s lead.  Because of this, the resonant frequency of the
+TD and its parasitics is around 3GHz and well damped.
+For any scope with less than about 1.5GHz BW, the ring would
+likely be invisible.
 * [http://w140.com/tek_067-0681-01.pdf Tektronix 067-0681-01 Datasheet (PDF)]